1. Field of the Invention
The present invention relates to a monitoring method using a CCD (Charge Coupled Device) imaging device, and a digital still camera using the monitoring method.
2. Description of the Background Art
Advances in the resolution of digital still cameras have recently implemented digital still cameras loaded with CCD imaging devices having 1,000,000 pixels or more. Such advanced digital still cameras include one loaded with an interline type CCD imaging device having 1,300,000 pixels and a mechanical shutter, and one capable of reading 1,300,000 pixels of its CCD imaging device at the same time.
However, an increase in the number of pixels of a CCD imaging device increases a period of time necessary for signals to be read out of the imaging device. For example, in a conventional digital still camera using an interline type CCD imaging device which belongs to a 400,000 pixels (640Hxc3x97480V) class, only {fraction (1/30)} second suffices even when all the pixels are read out at a rate of {fraction (1/60)} sec for one field. However, as for a digital still camera with an interline type CCD imaging device belonging to a 1,300,000 pixels (1,280Hxc3x971,024V) class, {fraction (1/7.5)} second is necessary for all the pixels to be read out at a rate of {fraction (1/15)} second for one field.
With a digital still camera, it is a common practice for the user of the camera to monitor the scene being picked up via, e.g., a liquid crystal (LC) monitor. At this instant, slow switching between consecutive pictures would perplex the user. In light of this, a digital still camera with a CCD imaging device having 1,300,000 or more pixels is usually operable either in a shoot mode for reading and recording all the pixels or in a monitor mode for reading only a part of the pixels. The monitor mode allows the user to confirm the angle of view and scene to be shot. In the monitor mode, the pixels of the imaging device from which signals should be read are reduced, or thinned, in the vertical direction so as to promote rapid drawing.
Another problem with the increasing number of pixels of the CCD imaging device is pixel defects including white spots, black spots, and dust. The number of pixel defects naturally increases with the increase in the number of pixels, causing the user to feel unpleasant. To solve this problem, it has been customary to store the addresses of pixel defects in a storage beforehand and to compensate for, in the shoot mode, the pixel defects of a picture written to a memory by interpolating pixels surrounding defective pixels. In the monitor mode, however, a picture read out of the CCD imaging device is directly output to a monitor without any compensation because the above interpolation scheme is time-consuming and because the monitor mode is a mode to confirm the scene to be shot. As a result, a number of defects in the form of spots often appear on the reduced or partial picture due to the pixel defects. Such defects always appear at the same positions on the monitor, obstructing the user""s view.
It is therefore an object of the present invention to provide a monitoring method with a CCD imaging device and capable of drawing on a monitor a picture with a minimum of influence of pixel defects in a monitor mode which effects vertical reduction or thinning, and a digital still camera using the monitoring method.
In accordance with the present invention, a monitoring method using a CCD imaging device having a multiphase electrode structure having a plurality of electrodes from which photoelectrically converted charges are output in response to stored charge transfer pulses has the steps of selecting one or two or more of the electrodes capable of minimizing the number of pixel defects in a picture to be monitored while being reduced in the vertical direction, and applying the stored charge transfer pulses only to the one or the two or more electrodes selected to thereby output a vertically thinned picture.
Also, in accordance with the present invention, a monitoring method using a CCD imaging device having a multiphase electrode structure having a plurality of electrodes from which photoelectrically converted charges are output in response to stored charge transfer pulses has the steps of switching one or two or more of the electrodes to thereby produce a plurality of pictures, allocating, based on the addresses of pixel defects present on the imaging device, the pixel defects to the plurality of pictures, totalizing the pixel defects picture by picture to thereby determine one picture including the smallest number of pixel defects, and applying the stored charge transfer pulses to one or two or more of the electrodes capable of producing the one picture to thereby output a vertically thinned picture to be monitored.
Further, in accordance with the present invention, a digital still camera includes a CCD imaging device having a multiphase electrode structure having a plurality of electrodes from which photoelectrically converted charges are output in response to stored charge transfer pulses. A selecting section selects one or two or more of the electrodes to which the stored charge transfer pulses should be applied in a monitor mode.
Moreover, in accordance with the present invention, a digital still camera includes a CCD imaging device having a multiphase electrode structure having a plurality of electrodes from which photoelectrically converted charges are output in response to stored charge transfer pulses. A storage stores pixel defects present on the imaging device in the form of addresses of the imaging device beforehand. A setting section switches one or two or more of the electrodes to thereby produce a plurality of pictures, allocates the pixel defects to the plurality of pictures on the basis of the addresses of pixel defects, totalizes the pixel defects picture by picture to thereby determine one picture including the smallest number of pixel defects, and applies the stored charge transfer pulses to one or two or more of the electrodes capable of producing the one picture to thereby output a vertically thinned picture to be monitored.
In addition, in accordance with the present invention, a digital still camera includes a CCD imaging device having a multiphase electrode structure having a plurality of electrodes from which photoelectrically converted charges are output in response to stored charge transfer pulses. A storage stores pixel defects present on the imaging device in the form of addresses of the imaging device beforehand. A setting section switches one or two or more of the electrodes to thereby produce a plurality of pictures, allocates the pixel defects to the plurality of pictures on the basis of the addresses of the pixel defects, totalizes the pixel defects picture by picture to thereby determine one picture including the smallest number of pixel defects, and applies the stored charge transfer pulses to one or two or more of the plurality electrodes capable of producing the one picture to thereby output a vertically thinned picture to be monitored. A controller causes, when the addresses stored in the storage are updated, the setting section to set the electrodes to which the stored charge transfer pulses should be applied at the time of monitoring.